First measurement of discrimination between helium and electron recoils in liquid xenon for low-mass dark matter searches

TL;DR

This study presents the first measurement of the ability to distinguish low-energy helium nuclear recoils from electron recoils in liquid xenon, which is crucial for advancing low-mass dark matter detection techniques.

Contribution

It provides the first experimental data on helium recoil discrimination in liquid xenon, aiding the development of low-mass dark matter search methods.

Findings

Helium recoils are well separated from electron recoils in liquid xenon.

The helium recoil population is offset from xenon nuclear recoils.

Results support the feasibility of using helium recoils in dark matter detection.

Abstract

We report the first measurement of discrimination between low-energy helium recoils and electron recoils in liquid xenon. This result is relevant to proposed low-mass dark matter searches which seek to dissolve light target nuclei in the active volume of liquid-xenon time projection chambers. Low-energy helium recoils were produced by degrading $\alpha$ particles from $^{210}$Po with a gold foil situated on the cathode of a liquid xenon time-projection chamber. The resulting population of helium recoil events is well separated from electron recoils and is also offset from the expected position of xenon nuclear recoil events.